After the baseline Cognitive Task Test and Virtual Driving Training session, the subjects underwent their planned surgery. The selection of the anesthetic gas was determined by a computer generated randomization list. The anesthesiologist or the CRNA in charge of the subject administered anesthesia. The investigators and the subjects were blinded to the anesthetic gas given. At the conclusion of the surgery, the anesthetic gas was shut down and the co-investigator was called into the OR to document the time the subjects take to open their eyes after the cessation of the gas.